JP 2001-173476 A describes an idle reduction technology as a countermeasure against exhaust emissions or for improvement of fuel efficiency, which stops an engine automatically when a vehicle stops and the engine is an idling state, and restarts the engine when the vehicle starts moving.
In a general steering-by-wire system, a backup clutch is installed for maintaining an engaged state without energization and a clutch is engaged when the engine is stopped by turning off an ignition. An operating sound of clutch engagement when turning off the ignition is hardly noticed, since it is caused in a scene of getting off the vehicle and since it blends into various noises caused for getting off the vehicle, such as a sound of releasing a door lock, or the like. On the other hand, the operating sound of clutch engagement may attract attention in an idle reduction state such as the above-mentioned prior art, since the noise is smaller than that in the scene of getting off the vehicle.